What ia an ERD. Define the RED related terms, including entities, attributes, cardinalities and relationships
An Entity Relationship (ER) Diagram is a form of flowchart that shows the relationships between "entities" like people, things, or concepts inside a system. ER Diagrams are most frequently used in the disciplines of software engineering, business information systems, education, and research to build or troubleshoot relational databases. They are also known as ERDs or ER Models, and they employ a predetermined collection of symbols to represent the interconnectivity of entities, connections, and their qualities. These symbols include rectangles, diamonds, ovals, and connecting lines. They have verbs for connections and nouns for entities, mirroring the grammatical framework.
In software engineering, an ER diagram is frequently the first step in determining requirements for an information systems project. Relational databases are modelled and designed using ER diagrams, both in terms of logic and business rules (in a logical data model) and in terms of the specific technology to be implemented (in a physical data model). Later, it is employed to simulate a specific database or databases. A relational database can theoretically be described that way as needed and has an equal relational table.
Entity:
An entity is a definite item that can have information recorded about it, such as a person, thing, concept, or event. Consider entities to be nouns. Examples include a client, student, vehicle, or good. usually shown as a rectangle.(smartdraw, 2022)
1)Entity type: A particular student or athlete, as opposed to a group of identifiable items, like students or athletes. Other instances include clients, vehicles, or goods.
2)Entity set: Similar to an entity type, but specified at a certain moment, for example, the students who were registered for the class on the first day. Other instances: Customers with vehicles currently registered in Florida who acquired them last month. The instance is a similar concept, where the particular person or vehicle would be an instance of the entity set.
Relationship:
The concept of "relationship" refers to how different entities influence or are related to one another. Relationships may be viewed as verbs. The stated student could sign up for a course, as an illustration. The relationship shown is the act of enrolling, which links the two things in this way. The two entities would be the student and the course. Normally, relationships are shown by diamonds or labels that are placed directly on the connecting lines.(smartdraw, 2022)
Attributes:
There are four types of attributes: simple, composite, derived, single-value, and multi-value. Simple: Denotes that the attribute value, such as a phone number, is atomic and cannot be further subdivided. Composite: An attribute gives rise to sub-attributes. Derived: An attribute is computed from another attribute, such as age from a birthday, or is somehow derived from that property.(smartdraw, 2022)
Cardinality:
Defines the numerical properties of the connection between two entities or entity sets. One-to-one, one-to-many, and many-to-many are the three fundamental cardinal connections. One student with one postal address would be an example of a one-to-one relationship. One student registers for numerous courses, but each of those courses has a single line leading back to that one student. This is an example of a one-to-many connection (or many-to-one, depending on the relationship orientation). Numerous faculty members are connected to a group of students, and multiple students are connected to a group of faculty members.(smartdraw, 2022)
References
lucidchart, 2022. What is an Entity Relationship Diagram (ERD)?. [online] Lucidchart. Available at: <https://www.lucidchart.com/pages/er-diagrams> [Accessed 8 September 2022].
smartdraw, 2022. Entity Relationship Diagram (ERD) - What is an ER Diagram?. [online] Smartdraw.com. Available at: <https://www.smartdraw.com/entity-relationship-diagram/> [Accessed 8 September 2022].
Comments
Post a Comment